Seat belt apparatus

ABSTRACT

A seat belt retractor, which is capable of winding and unwinding a seat belt for occupant restraint by an electric motor, warns a vehicle occupant. A seat belt retractor of a seat belt apparatus to be installed in a vehicle is structured such that a motor is controlled to repeat an action of increasing and decreasing the tension acting on a seat belt a plurality of times according to a setting that the seat belt tension at the initial stage of each action overshoots a predetermined target tension, for the purpose of warning a vehicle occupant who wears the seat belt.

BACKGROUND

The present invention relates to a technology for developing a seat beltretractor to be installed in a vehicle.

Conventionally, seat belt apparatuses of various structures forrestraining an occupant in a vehicle by a seat belt are known.

Japanese Unexamined Utility Model Publication No. H06-71333 (“JP Pub.No. '333”), which is incorporated by reference herein in its entirety,discloses a structure of a seat belt apparatus capable of winding andunwinding a seat belt by the driving of a motor or the like. With thetechnology disclosed in JP Pub. No. '333, a seat belt retractor employsa structure in which the winding and unwinding of the seat belt onto aspool is conducted by a motor and a structure in which the tension onthe seat belt is intermittently changed so as to change the restrainingforce by the action of the motor, thereby warning a driver about thepossibility of a vehicle collision.

SUMMARY

One embodiment of the invention relates to a seat belt retractor to beinstalled in a vehicle. The retractor comprises an electric motor; aspool which is capable of winding and unwinding a seat belt for occupantrestraint according to the driving of the electric motor; and a controlmechanism for controlling the electric motor. The control mechanismperforms a control mode in which the electric motor is controlled torepeat an action of increasing and decreasing the tension acting on theseat belt via the spool a plurality of times according to a setting thatthe seat belt tension at the initial stage of each action overshoots apredetermined target tension to warn a vehicle occupant wearing the seatbelt.

Another embodiment of the invention relates to a seat belt apparatus tobe installed in a vehicle. The apparatus comprises a seat belt foroccupant restraint which can be worn by a vehicle occupant; an electricmotor; a spool which is capable of winding and unwinding the seat beltaccording to the driving of the electric motor; a control mechanism tocontrol the electric motor; a buckle fixed to the vehicle; a tonguewhich is attached to the seat belt and is latched to the buckle when theseat belt is worn; and a detection sensor for detecting that the tongueis latched to the buckle. The detection sensor detects that the seatbelt is worn by the vehicle occupant, the control mechanism performs acontrol mode in which the electric motor is controlled to repeat anaction of increasing and decreasing the tension acting on the seat beltvia the spool a plurality of times according to a setting that thetension at the initial stage of each action overshoots a predeterminedtarget tension to warn the vehicle occupant.

Another embodiment of the invention relates to a vehicle. The vehiclecomprises an accommodating space; and seat belt apparatus accommodatedin the accommodating space. The seat belt apparatus includes a seat beltfor occupant restraint which can be worn by a vehicle occupant; anelectric motor; a spool which is capable of winding and unwinding theseat belt according to the driving of the electric motor; a controlmechanism to control the electric motor; a buckle fixed to the vehicle;a tongue which is attached to the seat belt and is latched to the bucklewhen the seat belt is worn; and a detection sensor for detecting thatthe tongue is latched to the buckle. The detection sensor detects thatthe seat belt is worn by the vehicle occupant, the control mechanismperforms a control mode in which the electric motor is controlled torepeat an action of increasing and decreasing the tension acting on theseat belt via the spool a plurality of times according to a setting thatthe tension at the initial stage of each action overshoots apredetermined target tension to warn the vehicle occupant.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory only,and are not restrictive of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become apparent from the following description, appendedclaims, and the accompanying exemplary embodiments shown in thedrawings, which are briefly described below.

FIG. 1 is an illustration showing the structure of a seat belt apparatusof an embodiment of the present invention.

FIG. 2 is an illustration showing the schematic structure of a seat beltretractor shown in FIG. 1.

FIG. 3 is a flow chart of the warning control process relating to thewarning mode of the seat belt retractor according to the embodiment.

FIGS. 4(a) and 4(b) are graphs showing changes with time in seat belttension actually acting on a vehicle occupant set according to anembodiment relating to the seat belt winding control shown in FIG. 3, inwhich FIG. 4(a) illustrates input seat belt tension and FIG. 4(b)illustrates output seat belt tension.

FIG. 5 is a graph showing changes with time in seat belt tension (input)set according to another embodiment of the warning control process.

FIGS. 6(a) and 6(b) are graphs showing changes with time in seat belttension actually acting on a vehicle occupant set according to acomparative example of the warning control process, in which FIG. 6(a)illustrates input seat belt tension and FIG. 6(b) illustrates outputseat belt tension.

FIG. 7 is a flow chart of the slack removing control process relating tothe belt winding and fitting mode of the seat belt retractor accordingto an embodiment.

FIGS. 8(a) and 8(b) are graphs showing changes with time in seat belttension actually acting on the vehicle occupant set according to theembodiment relating to the seat belt winding control shown in FIG. 7, inwhich FIG. 8(a) illustrates input seat belt tension and FIG. 8(b)illustrates output seat belt tension.

FIG. 9 is a graph showing changes with time in seat belt tension (input)set according to another embodiment of the slack removing controlprocess.

FIG. 10 is a graph showing changes with time in seat belt tension(input) set according to another embodiment of the slack removingcontrol process.

FIGS. 11(a) and 11(b) are graphs showing changes with time in seat belttension actually acting on a vehicle occupant set according to acomparative example of the slack removing control process, in which FIG.11(a) illustrates input seat belt tension and FIG. 11(b) illustratesoutput seat belt tension.

DETAILED DESCRIPTION

In order to warn a vehicle occupant about the possibility of a vehiclecollision by use of a seat belt apparatus as disclosed in theaforementioned JP Pub. No. '333, a motor control may be employed inwhich a motor is controlled to repeat an action of increasing thetension acting on a seat belt to a predetermined target value and thenreducing the tension several times at regular time intervals.

Though the aforementioned control enables a vehicle occupant to bewarned, it is difficult to conduct this motor control to exactly bringthe seat belt tension actually acting on the vehicle occupant close tothe predetermined target value. If a control for simply increasing thepreset value of the seat belt tension is employed in order to ensurethat the vehicle occupant is informed of the warning by the seat belt,only restraining feeling of the vehicle occupant caused by the seat beltmust be increased. On the other hand, if a control for simply decreasingthe preset value of the seat belt tension is employed, the restrainingfeeling caused by the seat belt can be reduced, but the absolute seatbelt tension will be insufficient so as to degrade the recognizabilityof warning.

It is an object of the present invention to provide a technology forcontrolling a seat belt retractor, which is capable of winding andunwinding a seat belt for occupant restraint, by use of an electricmotor and to therefore provide a technology effective for ensuring thewarning to draw a vehicle occupant's attention.

Embodiments of the present invention can be typically adapted to a seatbelt retractor to be installed in an automobile. In addition,embodiments of the present invention can be adapted to a technology fordeveloping a seat belt retractor to be installed in a vehicle other thanthe automobile, such as aircraft, boat, train, bus and the like.

The seat belt retractor of a first embodiment is a device to beinstalled in a vehicle and comprises at least an electric motor, aspool, and a control mechanism.

The spool is a member which is operated according to the driving of theelectric motor to wind or unwind a seat belt for occupant restraint. Theseat belt for occupant restraint to be wound onto and unwound from thespool is a long belt to be worn by a vehicle occupant seated in a seatand is sometimes called “webbing”. Typically, the vehicle occupantseated in the vehicle seat is restrained by the seat belt when restraintis required such as a vehicle collision. In the present embodiment, ifrequired, a power transmission mechanism may be suitably disposedbetween the electric motor and the spool to selectively achieve aconnected state where the electric motor and the spool are connected anda disconnected state where the connected state is cancelled.

The control mechanism is adapted at least as a mechanism for controllingthe driving of the electric motor and controls the driving direction,the driving time, the output of the electric motor and the like. Thecontrol mechanism is typically composed of a CPU (central processingunit), an input/output unit, a storage unit, a peripheral unit, and thelike. The control mechanism may be provided exclusively for the seatbelt retractor or used not only for the seat belt retractor but also forother control mechanisms for controlling the driving system and/orelectric system.

In embodiments of the present invention, the control mechanism performsa control mode in which the electric motor is controlled to repeat anaction of increasing and decreasing the tension acting on the seat beltvia the spool (temporarily increasing the tension) a plurality of timesin order to surely warn a vehicle occupant (typically a driver) whowears the seat belt. By performing the control mode, warning isconducted to the vehicle occupant so as to draw the vehicle occupant'sattention. Specifically, when it is determined that an obstacle (anothervehicle, object, pedestrian or the like) exists within a predeterminedrange around the subject vehicle or that the subject vehicle is highlylikely to collide with the obstacle, or when it is determined that thedriver dozes, the warning is conducted. That is, the seat belt retractorhas a function as a restraint mechanism for restraining the vehicleoccupant by the seat belt and, in addition, a function as a warningmechanism (warning system) for warning the vehicle occupant by mechanismof the seat belt.

When the warning is conducted to the vehicle occupant by the windingaction of the seat belt, it is difficult to exactly bring the seat belttension actually acting on the vehicle occupant close to the targetvalue preset in the motor control. If a control for simply increasingthe preset value of the seat belt tension is employed in order to ensurethat the vehicle occupant is informed of the warning by the seat belt,only restraining feeling of the vehicle occupant caused by the seat beltmust be increased.

In embodiments of the present invention, therefore, the controlmechanism is adapted to perform at least a control mode for controllingthe electric motor to be driven according to such a setting that thetension at the initial stage of the action increasing and decreasing thetension acting on the seat belt overshoots the target tension. Withregard to the overshoot, the curve indicating changes with time in thepreset tension is adapted to have an extreme value, which slightlyexceeds the target value, at the initial stage of each action. Thiscontrol mode is achieved by changing the current value (sometimesreferred to as “control current value”) and/or the voltage value(sometimes referred to as “applied voltage value”) of the electric motorto control the motor output so as to set the speed and/or accelerationof winding of the seat belt to desired level. The target tension may bepreviously set or set according to a result of judgment of the body sizeor the clothes of the vehicle occupant on a case-by-case basis.

Therefore, according to the aforementioned structure of the seat beltretractor as claimed in the first embodiment, the seat belt tensionactually acting on the vehicle occupant can be rapidly increased to thetarget tension and, except the initial stage of each warning action, therestraining feeling caused by the seat belt can be prevented from beingincreased needlessly. Accordingly, it is capable of surely conductingthe warning to draw the vehicle occupant's attention. Further,embodiments of the invention enable the warning by use of the seat belteasily without complicating the control.

The seat belt apparatus of a second embodiment is an apparatus to beinstalled in a vehicle and comprises at least a seat belt, an electricmotor, a spool, a control mechanism, a buckle, a tongue, and a detectionsensor.

The seat belt is a long belt to be worn by a vehicle occupant seated ina seat and is sometimes called “webbing”. Typically, the vehicleoccupant seated in the vehicle seat is restrained by the seat belt whenrestraint is required such as a vehicle collision. The buckle is amember fixed to the vehicle. The tongue is a member which is attached tothe seat belt and is latched to the buckle when the seat belt is worn bythe vehicle occupant. The detection sensor is a mechanism for detectingthat the tongue is latched to the buckle. The electric motor, the spool,and the control mechanism of this embodiment have substantially the samefunctions as those of the seat belt retractor of the first embodiment.

That is, the seat belt apparatus of this embodiment has a function as arestraint mechanism for restraining the vehicle occupant by the seatbelt and, in addition, a function as a warning mechanism (warningsystem) for warning the vehicle occupant by use of the seat belt. Inthis embodiment, the control mechanism is adapted to perform at least acontrol mode for controlling the electric motor to be driven accordingto such a setting that the tension at the initial stage of the actionincreasing and decreasing the tension acting on the seat belt overshootsa predetermined target tension.

Therefore, according to the aforementioned structure of the seat beltapparatus of the second embodiment, warning a vehicle occupant can beconducted by the seat belt.

The vehicle with a seat belt apparatus of a third embodiment comprisesat least a seat belt apparatus as described in the second embodiment. Inthe vehicle of the embodiment, the seat belt apparatus is accommodatedin an accommodating space in the vehicle such as an accommodating spacein a pillar, an accommodating space in a seat, or an accommodating spacein another part of the vehicle.

Accordingly, the third embodiment provides a vehicle in which a seatbelt apparatus is accommodated in an accommodating space in the vehicle,wherein the seat belt apparatus can warn and draw the occupant'sattention via the seat belt.

As described in the above, embodiments of the present invention relateto the structure of a seat belt system for winding or unwinding a seatbelt for occupant restraint according to the driving of an electricmotor and can control the electric motor to be driven according to sucha setting that the tension at the initial stage of the action ofincreasing and decreasing the tension acting on the seat belt overshootsthe predetermined target tension, thereby surely conducting the warningfor drawing the vehicle occupant's attention.

Hereinafter, embodiments of the present invention will be described indetail with reference to drawings. First, description will be made asregard to an embodiment of the present invention with reference to FIG.1 and FIG. 2.

FIG. 1 is an illustration showing the structure of a seat belt apparatus100 as an embodiment of “the seat belt apparatus” according to thepresent invention. FIG. 2 is an illustration showing the schematicstructure of a seat belt retractor 1 shown in FIG. 1.

As shown in FIG. 1, the seat belt apparatus 100 of this embodiment is aseat belt apparatus for a vehicle to be installed in an automotivevehicle as “a vehicle with a seat belt apparatus” of the presentinvention and mainly consists of a seat belt retractor 1, a seat belt 3,a shoulder guide anchor 10, a tongue 12, an outer anchor 14, a buckle16, an ECU 20 and the like. In addition, an input element 30 isinstalled in the vehicle to detect information about collisionprediction or collision occurrence of the vehicle, information about thedriving state of the vehicle, information about the sitting position andthe body size of a vehicle occupant seated in a seat, information abouttraffic conditions around the vehicle, information about weathercondition and about time zone, and the like and to input such detectedinformation to the ECU 20. The detected information of the input element30 is transmitted to the ECU 20 anytime or at predetermined intervalsand is used for the operation control of the seat belt apparatus 100 andthe like.

Particularly, the input element 30 of this embodiment includes acollision information detection sensor 32 for detecting informationabout a vehicle collision such as a prediction of a vehicle collisionand an occurrence of actual vehicle collision. The collision informationdetection sensor 32 is a sensor capable of detecting (measuring)distance, speed, and acceleration of a collision object (anothervehicle, object, pedestrian or the like) relative to the subject vehicleand also detecting (measuring) accelerations or the like in three-axial(X-axis, Y-axis, and Z-axis) directions acting on the subject vehicle.The collision information detection sensor 32 may be composed of asingle detection sensor or a combination of plural detection sensors.Specifically, millimeter wave radar, laser radar, acceleration sensor,camera sensor and the like may be used as the collision informationdetection sensor 32.

The seat belt 3 is a long belt (webbing) to be used for restraining avehicle occupant C (sometimes referred to as “driver”) seated in avehicle seat 40 as a driver's seat. The seat belt 3 corresponds to the“seat belt for occupant restraint” in embodiments of the presentinvention. The seat belt 3 is withdrawn from the seat belt retractor 1fixed relative to the vehicle and extends through a shoulder guideanchor 10 provided around an area about the shoulder of the vehicleoccupant C and is connected to an outer anchor 14 through a tongue 12.The shoulder guide anchor 10 has a function of holding the seat belt 3to the area about the shoulder of the occupant C and guiding the seatbelt 3. By inserting (latching) the tongue 12 to the buckle 16 fixed tothe vehicle body, the seat belt 3 becomes into the state worn by thevehicle occupant C. The tongue 12 corresponds to the “tongue” inembodiments of the present invention and the buckle 16 to which thetongue 12 can be latched corresponds to the “buckle” in embodiments ofthe present invention.

The buckle 16 has a built-in buckle switch 16a. The buckle switch 16 adetects that the tongue 12 is inserted into the buckle 16 so as toconnect the seat belt to the buckle (actually, detects that the seatbelt becomes into the worn state). The information detected by thebuckle switch 16 a is transmitted to the ECU 20 which determines whetheror not the seat belt 3 is in the worn state. The buckle switch 16 acorresponds to the “detection sensor for detecting that the tongue islatched to the buckle” in embodiments of the present invention.

The seat belt retractor 1 is a device capable of performing the actionof winding or unwinding the seat belt 3 via a spool 5 and a motor 7 aswill be described later and corresponds to the “seat belt retractor” inembodiments of the present invention. The seat belt retractor 1 isinstalled in an accommodating space in a B-pillar 42 of the vehicle inthe embodiment shown in FIG. 1.

The ECU 20 has a function of conducting the control of the seat beltretractor 1 and other operational mechanisms based on the input signalsfrom the input element 30 and comprises a CPU (Central processing unit),an input/output unit, a storage unit, a peripheral unit, and the like.Particularly in this embodiment, the ECU 20 controls the motor 7, aswill be described later, of the seat belt retractor 1. Specifically, theECU 20 controls the amount of current supplied to an electromagneticcoil of the motor 7 and the direction of the current supply so as tovary the rotational speed, the rotational direction, the rotationalperiod of time, and the rotational torque (output) of a shaft of themotor 7. The ECU 20 is structured as a mechanism for controlling thedriving of the motor 7 and controlling a power transmission mechanism 9,as will be described later, to switch between the state where the powerof the motor 7 is transmitted to the spool 5 and the state where thepower is not transmitted to the spool 5. The details will be describedlater. Further, the ECU 20 is also provided with a function of detecting(measuring) the current value of the motor 7 in operation. The ECU 20corresponds to the “control mechanism” in embodiments of the presentinvention.

The ECU 20 may be exclusive to the seat belt retractor 1 or used notonly for the seat belt retractor 1 but also for other control mechanismsfor controlling driving system and/or electric system.

The spool 5 as shown in FIG. 2 is formed in a columnar or cylindricalshape of which outer periphery (seat belt contact face) functions as thewind-up surface on which the seat belt 3 is wound. The spool 5 is amember for performing the winding action and unwinding action of theseat belt 3 for occupant restraint according to the driving of the motor7 as the “electric motor” in embodiments of the present invention. Thespool 5 corresponds to the “spool” in embodiments of the presentinvention.

In this embodiment, the power transmission mechanism 9 is arrangedbetween the spool 5 and the motor 7. The power transmission mechanism 9is a mechanism capable of taking a connected state where the spool 5 andthe motor 7 are connected (power transmission operation mode) and adisconnected state where the connected state is cancelled (powertransmission disconnection mode). The power transmission mechanism 9 issometimes referred to as so-called “clutch” which are composed of acombination of gears. The connected state of the power transmissionmechanism 9 is a state where the power of the motor 7 is allowed to betransmitted to the spool via the power transmission mechanism 9. Whenthe motor 7 is driven in this connected state, the power of the motor 7is transmitted to the spool 5 via the power transmission mechanism 9.During this, the rotational speed of the motor 7 is reduced by the powertransmission mechanism 9. On the other hand, in the disconnected stateof the power transmission mechanism 9, the physical connection betweenthe spool 5 and the motor 7 is cancelled so as to allow the easyunwinding (withdrawing) of the seat belt 3 from the spool 5. It shouldbe noted that the spool 5 and the motor 7 may be directly connectedwithout the power transmission mechanism 9 between the spool 5 and themotor 7, if required.

In this embodiment, the power transmission mechanism 9 is constructed asa so-called “single-stage clutch”, but not illustrated. Accordingly,when the motor 7 is driven with a predetermined motor output in thepower transmission operation mode of the power transmission mechanism 9,the rotation of the motor 7 is transmitted to the spool 5 with therotational speed being reduced so that the spool 5 is driven to rotatewith predetermined rotational torque at predetermined rotational speed.

Instead of the power transmission mechanism 9, a power transmissionmechanism capable of changing the rotational torque and the rotationalspeed of the spool into several stages may be employed. For example, incase of a two-stage clutch capable of changing the rotational torque andthe rotational speed of the spool into two stages, the powertransmission mechanism can be set in a high-reduction ratio mode withrelatively high rotational torque and relatively low rotational speed inorder to respond to a need for winding of the seat belt onto the spoolwith large belt tension. On the other hand, the power transmissionmechanism can be set in a low-reduction ratio mode with relatively lowrotational torque and relatively high rotational speed in order torespond to a need for rapid winding of the seat belt onto the spool.

In this embodiment, the seat belt retractor 1 of this embodiment has thefollowing seven seat belt setting modes of the seat belt 3. Based onthese seat belt setting modes, the control of the motor 7 and the powertransmission mechanism 9 are performed by the ECU 20.

(1) Belt Storage Mode

Belt storage mode is a mode in which the seat belt 3 is not used andfully wound onto the spool 5. In the seat belt retractor 1 in the beltstorage mode, the motor 7 is not driven and the power transmissionmechanism 9 is set to the power transmission disconnection mode.Therefore, only very weak belt tension is applied to the seat belt 3 andthe power consumption is zero.

(2) Belt Withdrawing Mode

Belt withdrawing mode is a mode in which the seat belt 3 is withdrawnfrom the spool 5 so as to be worn by the occupant. The seat beltretractor 1 in the belt withdrawing mode is also set in the powertransmission disconnection mode. Therefore, the seat belt 3 can bewithdrawn with small force. Also in this case, the motor 7 is not drivenso that the power consumption is zero.

(3) Belt Winding and Fitting Mode

Belt winding and fitting mode is a mode in which after the seat belt 3is withdrawn and the tongue (the tongue 12 in FIG. 1) is inserted intoand latched with the buckle to turn ON the buckle switch (the buckleswitch 16 a in FIG. 1), excessively withdrawn part of the seat belt 3 iswound in order to fit the seat belt 3 to the occupant. Alternatively,the belt winding and fitting mode is a mode in which when the occupantmoves so as to withdraw a predetermined amount of the seat belt 3 fromthe normally worn state of the seat belt 3 (at this point, the buckleswitch is in the ON state) and then the occupant returns to the originalposition, the withdrawn part of the seat belt 3 is wound. In the seatbelt retractor 1 in the belt winding and fitting mode, the motor 7 isdriven to rotate at high rotational speed in the belt winding directionand the power transmission mechanism 9 is set to the power transmissionoperation mode. Therefore, the seat belt 3 is rapidly wound onto thespool 5 and then the motor 7 is stopped when very weakly predeterminedbelt tension is generated, whereby the seat belt 3 is worn by and fittedto the occupant.

(4) Normal Wearing Mode (Comfortable Mode)

Normal wearing mode (comfortable mode) is a mode in which the occupantwears the seat belt 3 in the normal state after the belt winding andfitting mode is terminated. In the seat belt retractor 1 in the normalwearing mode, the motor 7 is not driven and the power transmissionmechanism 9 is set in the power transmission disconnection mode.Therefore, only very weak belt tension is applied to the seat belt 3 sothat the vehicle occupant can wear the seat belt 3 without any stress.In addition, the power consumption is zero.

(5) Warning Mode

Warning mode is a mode in which when the system detects dozing of thedriver during running or detects an obstacle around the vehicle when theseat belt is in the normal wearing mode during running, the seat belt 3is wound repeatedly predetermined times so as to warn the driver. In theseat belt retractor 1 in the warning mode, the motor 7 is controlled tobe driven repeatedly. Therefore, the operation of applying relativelystrong belt tension (which is weaker than that of the belt tensionduring the emergency mode as will be described later) and very weak belttension onto the seat belt 3 is alternately repeated, thereby drawingthe driver's attention to the dozing and the obstacle around thevehicle. The detailed process of the control in the aforementioned“warning mode” will be described later.

(6) Emergency Mode

Emergency mode is a mode which is set when the vehicle is extremelylikely to have a collision with an obstacle or the like during runningin the normal wearing mode or following the aforementioned warning mode.In the seat belt retractor 1 in the emergency mode, the powertransmission mechanism 9 is set in the power transmission operation modeand the motor 7 is controlled to rotate at high rotational speed withhigh rotational torque in the belt winding direction. Therefore, themotor 7 is stopped when predetermined extremely strong belt tension isgenerated on the seat belt 3 after the seat belt 3 is rapidly wound ontothe spool 5, thereby securely restraining the vehicle occupant with theseat belt 3.

(7) Belt Winding and Storing Mode

Belt winding and storing mode is a mode for fully winding up the seatbelt 3 such that the seat belt 3 becomes into the storage state when thetongue (the tongue 12 in FIG. 1) is released from the buckle forcanceling the wearing of the seat belt 3 so that the buckle switch (thebuckle switch 16 a in FIG. 1) becomes OFF. In the seat belt retractor 1in the belt winding and storing mode, the power transmission mechanism 9is set to the power transmission operation mode and the motor 7 iscontrolled to rotate in the belt winding direction. Accordingly, thewithdrawn seat belt 3 is promptly wound onto the spool 5. Thus, themotor 7 is stopped when the seat belt 3 is fully wound and apredetermined belt tension which is very weak is developed, whereby theseat belt 3 becomes to the belt storage mode in which the aforementionedvery weak belt tension is applied to the seat belt 3.

With respect to the control of the seat belt retractor 1 having theaforementioned structure, the detailed process of the control in theaforementioned “warning mode” will be described in detail with referenceto FIG. 3 through FIG. 5. The control in the seat belt retractor 1 isconducted by the ECU 20 as shown in FIG. 1 and FIG. 2.

FIG. 3 is a flow chart of the warning control process relating to thewarning mode of the seat belt retractor 1 according to the embodiment.

In the warning control process shown in FIG. 3, in step S10, it isdetermined whether or not the seat belt is worn. Specifically, when thebuckle switch 16 a as shown in FIG. 1 detects that the tongue 12 isinserted and latched to the buckle 16, it is determined that the seatbelt is worn. When the buckle switch 16 a detects that the latching ofthe tongue 12 is cancelled, it is determined that the wearing of theseat belt is cancelled.

When it is determined that the seat belt is worn in step S10 (YES instep S10), the process proceeds to step S20. On the other hand, when itis determined that the wearing of the seat belt is cancelled in step S10(NO in step S10), the warning control process is terminated without anyaction.

In step S20 shown in FIG. 3, it is determined whether or not the warningcondition is satisfied. Specifically, when it is determined, based oninformation detected by the collision information detection sensor 32 inFIG. 1, that an obstacle (another vehicle, object, pedestrian or thelike) around the vehicle exists within a predetermined range or that thesubject vehicle is highly likely to collide with the obstacle, or whenit is determined, based on information detected by a sensor fordetecting the tension acting on the seat belt, that the driver dozes, itis determined that the warning condition is satisfied.

When it is determined that the warning condition is satisfied in stepS20 (YES in step S20), the process proceeds to step S30 where the seatbelt winding control is conducted and then the warning control processis terminated. On the other hand, when it is determined that the warningcondition is not satisfied in step S20 (NO in step S20), the warningcontrol process is terminated without any action.

In step S30 shown in FIG. 3, the seat belt winding control in thewarning mode is conducted. In the seat belt winding control, the motor 7is controlled to repeat the action of increasing and decreasing thetension acting on the seat belt 3 (temporarily increasing the tension) aplurality of times, thereby warning the vehicle occupant (driver). Thiscontrol corresponds to “the electric motor is controlled to repeat anaction of increasing and decreasing the tension acting on the seat beltvia the spool a plurality of times . . . so as to surely warn a vehicleoccupant who wears the seat belt” in embodiments of the presentinvention.

By the way, when conducting the warning to the vehicle occupant by theaforementioned winding action of the seat belt 3, it is difficult toconduct this motor control to exactly increase the seat belt tensionactually acting on the vehicle occupant to the predetermined targetvalue. As a comparative example, FIG. 6 shows changes with time in seatbelt tension (input) which is set to repeatedly provide a constanttarget tension Ta for a predetermined period of time (Δt) and changeswith time in seat belt tension (output) actually acting on the vehicleoccupant. As shown in FIG. 6, if the action increasing the seat belttension a plurality of times (three times in FIG. 6) is set such thatthe wave indicating the changes with time in seat belt tension is arectangular wave (square wave), the rising of tension at the initialstage of each action is significantly suppressed.

Therefore, this embodiment employs a control method of bringing thetension at the initial stage of each action close to the predeterminedtarget tension Ta as exactly as possible by devising the setting of theseat belt tension (input).

FIG. 4 shows changes with time in seat belt tension (input) and changeswith time in seat belt tension (output) actually acting on the vehicleoccupant according to this embodiment.

As shown in FIG. 4, this embodiment employs a control mode in which themotor 7 is controlled according to such a setting that the tension atthe initial stage of each action overshoots the predetermined targettension Ta to reach a tension Tb. With regard to the overshoot, thecurve indicating changes with time in the preset tension is adapted tohave an extremely value (tension Tb), which slightly exceeds the targetvalue Ta, at the initial stage of each action. Specifically, the belttension (input) is increased to the tension Tb, higher than the targettension Ta, at time points t1, t3, and t5 and is then graduallydecreased to the target tension Ta until time points t2, t4, and t6.This control corresponds to “the electric motor is controlled . . .according to a setting that the tension at the initial stage of eachaction overshoots a predetermined target tension” in embodiments of thepresent invention. This control mode is achieved by changing the currentvalue (sometimes referred to as “control current value”) and/or thevoltage value (sometimes referred to as “applied voltage value”) of themotor 7 to control the motor output so as to set the speed and/oracceleration of winding of the seat belt 3 to desired level.

According to the aforementioned control method, as shown in the lowergraph of FIG. 4, the rising of tension at the initial stage of each ofthe actions of plural times (three times in FIG. 4) for increasing theseat belt tension can be increased than that of the comparative examplewhich is shown by two-dot chain line, thereby bringing the tension atthe initial stage of each action close to the predetermined targettension Ta as exactly as possible.

The setting tensions Ta and Tb used in the control may be suitably setaccording to a result of judgment of the body size or the clothes of thevehicle occupant.

With regard to the setting for making the seat belt tension (input)overshooting the target tension, a variety of settings may be used, ifrequired. For example, instead of the setting as shown in the uppergraph of FIG. 4, a setting of another embodiment as shown in FIG. 5 maybe employed. In this setting, the belt tension (input) is increased tothe tension Tb, higher than the target tension Ta, at time points t1,t3, and t5 and is then decreased stepwise to the target tension Ta untiltime points t2, t4, and t6. Also by this control, the tension at theinitial stage of each action can be raised as shown in the lower graphof FIG. 4.

According to the seat belt retractor 1 of this embodiment as describedin the above, the warning control process shown in FIG. 3 is conductedby the setting as shown in FIG. 4 or FIG. 5, thereby ensuring that thevehicle occupant is aware of warning by seat belt 3. This can urge thedriver to take operation required for avoiding a vehicle collision andcall the vehicle occupant's attention when the vehicle occupant dozes.Though shown in either of FIG. 4 and FIG. 5 is a case where the actionincreasing and decreasing the tension acting on the seat belt 3(temporarily increasing the tension) is repeated three times, thepresent invention may suitably employ a setting in which the action isrepeated twice or a setting in which the action is repeated four timesor more.

In this embodiment, the warning control process shown in FIG. 3 isfollowed by such a control that when it is determined, based oninformation detected by the collision information detection sensor 32,that the subject vehicle is highly likely to collide with the obstacleor the like, the process proceeds to the aforementioned emergency mode.In the emergency mode, the motor 7 is stopped when predeterminedextremely strong belt tension is finally generated on the seat belt 3,thereby securely restraining the vehicle occupant with the seat belt 3.

FIG. 7 is a flow chart of the slack removing control process relating tothe belt winding and fitting mode of the seat belt retractor 1 accordingto the embodiment.

In the retractor control process shown in FIG. 7, in step S110, it isdetermined whether or not the seat belt is worn. Specifically, when thebuckle switch 16 a as shown in FIG. 1 detects that the tongue 12 isinserted and latched to the buckle 16, it is determined that the seatbelt is worn. When the buckle switch 16 a detects that the latching ofthe tongue 12 is cancelled, it is determined that the wearing of theseat belt is cancelled.

When it is determined that the seat belt is worn in step S110 (YES instep S110), the process proceeds to step S120. On the other hand, whenit is determined that the wearing of the seat belt is cancelled in stepS110 (NO in step S110), the slack removing control process is terminatedwithout any action.

In step S120 shown in FIG. 7, it is determined whether or not thewinding start condition has been satisfied (or is satisfied).Specifically, when it is determined, based on information detected by asensor for detecting change in tension acting on the seat belt 3, thatthe seat belt 3 has been kept in unwound state or that the seat belt 3is kept in unwound state, it is determined that the winding startcondition has been satisfied (or is satisfied).

When it is determined that the winding start condition has beensatisfied (or is satisfied) in step S120 (YES in step S120), the processproceeds to step S130 where the seat belt winding control is conductedand then the slack removing control process is terminated. On the otherhand, when it is determined that the winding start condition is notsatisfied in step S120 (NO in step S120), the slack removing controlprocess is terminated without any action.

In step S130 shown in FIG. 7, the seat belt winding control in the beltwinding and fitting mode is conducted. In the seat belt winding control,the motor 7 is controlled to perform the action of increasing anddecreasing the tension acting on the seat belt 3 (temporarily increasingthe tension), thereby winding up the seat belt 3 which has beenexcessively unwound from the spool 5.

By the way, for removing the slack of the seat belt 3 by theaforementioned winding action, it is required to increase the seat belttension. If the seat belt tension is simply increased without anyparticular arrangement, the slack of the seat belt can be removed, butthe restraining feeling of the vehicle occupant caused by the seat beltis increased. As a comparative example, FIG. 11 shows changes with timein seat belt tension (input) which is set to provide a constant targettension Ta for a predetermined period of time and changes with time inseat belt tension (output) actually acting on the vehicle occupant. Asshown in FIG. 11, if the action increasing the seat belt tension is setsuch that the wave indicating the changes with time in seat belt tensionis a rectangular wave (square wave), the rising of tension at theinitial stage of the action is significantly sudden, leading to thesudden tightness to the vehicle occupant.

Therefore, this embodiment employs a control method of controlling therising of tension at the initial stage of the action of increasing theseat belt tension as soft as possible by devising the setting of theseat belt tension (input).

FIG. 8 shows changes with time in seat belt tension (input) and changeswith time in seat belt tension (output) actually acting on the vehicleoccupant according to this embodiment.

This embodiment as shown in FIG. 8 employs a control mode in which themotor 7 is controlled to be driven according to such a setting that, atthe initial stage of the action of increasing the seat belt tension, thetension increasing rate until the seat belt tension reaches the targettension Ta is lower than a predetermined criterion value of restrainingforce. Specifically, the inclination L2 of rising curve of the seat belttension from time s1 to time s2 in the upper graph of FIG. 8 is adaptedto be gentler than the inclination L1 of the reference linecorresponding to the rising of the seat belt tension in the upper graphof FIG. 11. This control mode is achieved by changing the current value(sometimes referred to as “control current value”) and/or the voltagevalue (sometimes referred to as “applied voltage value”) of the motor 7to control the motor output so as to set the speed and/or accelerationof winding of the seat belt 3 to desired level.

According to the aforementioned control method, as shown in the lowergraph of FIG. 8, a rising curve L3 of seat belt tension in which therising of tension at the initial stage of the action as the slackremoving action of increasing the seat belt tension is gentle is formed.Therefore, the restraining feeling of the vehicle occupant caused by theseat belt 3 can be controlled to be as little as possible.

The setting tensions Ta used in the control may be suitably setaccording to a result of judgment of the body size or the clothes of thevehicle occupant.

With regard to the setting for making the rising rate of tension untilthe seat belt tension reaches the target tension at the initial stage ofthe seat belt winding action to be lower than the predeterminedcriterion value of restraining force, a variety of settings may be used,if required. For example, instead of the setting as shown in the uppergraph of FIG. 8, a setting of another embodiment as shown in FIG. 9 orFIG. 10 may be employed.

In the embodiment shown in FIG. 9, the seat belt tension is increasedstepwise to the target tension Ta so that the average inclination L4 ofa rising curve of seat belt tension from time s1 to time s2 is gentlerthan the inclination L1 of the reference line corresponding to therising of the seat belt tension shown in the upper graph of FIG. 11. Inthe embodiment shown in FIG. 10, the seat belt tension is increasedcontinuously (in a curved line) to the target tension Ta so that theaverage inclination L5 of a rising curve of seat belt tension from times1 to time s2 is gentler than the inclination L1 of the reference linecorresponding to the rising of the seat belt tension shown in the uppergraph of FIG. 11. By either of these settings, as shown in the lowergraph of FIG. 8, a rising curve L3 of seat belt tension in which therising of tension at the initial stage of the action as the slackremoving action of increasing the seat belt tension is gentle is formed.Therefore, the restraining feeling of the vehicle occupant caused by theseat belt 3 can be controlled to be as little as possible.

According to the seat belt retractor 1 of this embodiment, the slackremoving control process shown in FIG. 7 is conducted according to anyone of the settings as shown in FIG. 8 through FIG. 10, thereby ensuringthe removal of slack of the seat belt and minimizing the increase inrestraining feeling of the vehicle occupant caused by the seat belt 3.

The present invention is not limited to the aforementioned embodiments,so various variations and modifications may be made. For example, thefollowing embodiments as variations of the aforementioned embodimentsmay be carried out.

The above embodiments have been described with regard to the seat beltretractor 1 to be installed in an automobile, the seat belt retractorcan be adapted to seat belt apparatuses to be installed in a vehicle fortransfer of occupant(s) such as an automobile, aircraft, boat, train,bus and the like.

Japan Priority Application 2005-228610, filed Aug. 5, 2005 including thespecification, drawings, claims and abstract, is incorporated herein byreference in its entirety.

Given the disclosure of the present invention, one versed in the artwould appreciate that there may be other embodiments and modificationswithin the scope and spirit of the invention. Accordingly, allmodifications attainable by one versed in the art from the presentdisclosure within the scope and spirit of the present invention are tobe included as further embodiments of the present invention. The scopeof the present invention is to be defined as set forth in the followingclaims.

1. A seat belt retractor to be installed in a vehicle comprising: anelectric motor for driving a spool; wherein the spool is configured towind and unwind a seat belt for restraining a vehicle occupant; and acontrol mechanism for controlling the electric motor, wherein thecontrol mechanism is configured to control the spool via the electricmotor so that the tension acting on the seat belt is increased anddecreased a plurality of times, and wherein the control mechanism isconfigured so that during the action of increasing the seat belt tensionthe seat belt tension exceeds a predetermined target tension in order towarn a vehicle occupant wearing the seat belt.
 2. The seat beltretractor according to claim 1, further comprising a power transmissionmechanism arranged between the electric motor and the spool toselectively connect or disconnect the electric motor and the spool.
 3. Aseat belt apparatus to be installed in a vehicle comprising: a seat beltfor occupant restraint which can be worn by a vehicle occupant; anelectric motor; a spool which is capable of winding and unwinding theseat belt according to the driving of the electric motor; a controlmechanism to control the electric motor; a buckle fixed to the vehicle;a tongue which is attached to the seat belt and is latched to the bucklewhen the seat belt is worn; and a detection sensor for detecting thatthe tongue is latched to the buckle, wherein when the detection sensordetects that the seat belt is worn by the vehicle occupant, the controlmechanism is configured to control the electric motor to repeatedlyincrease the tension on the seat belt to a value greater than apredetermined target tension to thereby warn the vehicle occupant. 4.The seat belt apparatus according to claim 3, further comprising a powertransmission mechanism arranged between the electric motor and the spoolto selectively connect or disconnect the electric motor and the spool.5. The seat belt apparatus according to claim 3, wherein when theretractor is in a warning mode to warn a vehicle occupant, the seat beltis repeatedly wound and unwound a predetermined number of times by theelectric motor between a warning tension and a weak tension.
 6. The seatbelt apparatus according to claim 5, wherein the warning mode occurswhen an obstacle is detected or a vehicle driver is detected to beasleep.
 7. The seat belt apparatus according to claim 5, wherein anemergency mode occurs when a collision with an obstacle is detected, andin the emergency mode the electric motor stops when a predeterminedamount of emergency tension is generated on the seat belt after the seatbelt is wound onto the spool.
 8. The seat belt apparatus according toclaim 7, wherein the emergency tension is greater than the warningtension.
 9. A vehicle comprising: seat belt apparatus accommodated in anaccommodating space, wherein the seat belt apparatus includes: a seatbelt for occupant restraint which can be worn by a vehicle occupant; anelectric motor for driving a spool which is capable of winding andunwinding the seat belt; a control mechanism to control the electricmotor; a buckle fixed to the vehicle; a tongue which is attached to theseat belt and is latched to the buckle when the seat belt is worn; and adetection sensor for detecting that the tongue is latched to the buckle;wherein when the detection sensor detects that the tongue is latched,the control mechanism is configured to control the electric motor torepeat an action of increasing and decreasing the tension acting on theseat belt via the spool a plurality of times, and wherein during eachaction the tension is increased to overshoot a predetermined targettension to thereby warn the vehicle occupant.
 10. The vehicle accordingto claim 9, wherein the accommodating space is a B-pillar of thevehicle.
 11. The vehicle according to claim 9, further comprising apower transmission mechanism arranged between the electric motor and thespool to selectively connect or disconnect the electric motor and thespool.
 12. The vehicle according to claim 9, wherein when the retractoris in a warning mode to warn a vehicle occupant, the seat belt isrepeatedly wound a predetermined number of times by the electric motorbetween a warning tension and a weak tension.
 13. The vehicle accordingto claim 12, wherein the warning mode occurs when an obstacle isdetected or a vehicle driver is detected to be asleep.
 14. The vehicleaccording to claim 12, wherein an emergency mode occurs when a collisionwith an obstacle is detected, and in the emergency mode the electricmotor stops when a predetermined amount of emergency tension isgenerated on the seat belt after the seat belt is wound onto the spool.15. The vehicle according to claim 14, wherein the emergency tension isgreater than the warning tension.